Lance Bass sacrificed watching Beauty and the Beast to hit up Sin City and check out the boy band’s “Larger Than Life” residency show at Planet Hollywood on Saturday, and fans were freaking out when the 37-year-old crooner got pulled on stage by AJ McLean during the group’s hit, “Shape Of My Heart.”

“I couldn’t believe it was happening -- I never thought I’d see my two favorites on one stage together!” enthused one fan after the show at the AXIS Theater.

“It was really great to see him and his husband having such a great time at the show, considering all the misconceptions about the whole BSB/*NYSNC rivalry over the years,” added another concert-goer. “And Lance looked amazing. He seems to have the fountain of youth!”

Justin Segura

Justin Segura

During the final gig in the band’s first leg of their Las Vegas residency run, McLean made a beeline for Bass, who was seated in the VIP area alongside his husband, Michael Turchin, and members of Brian Littrell and Kevin Richardson’s families.

Pulling the My Kitchen Rules star onto the catwalk, McLean then escorted him arm-in-arm onto the main stage, where the group serenaded the singer and television personality as he clutched his heart.

As McLean returned to the crowd to hand out a red rose, Bass remained centerstage where he high-fived Howie Dorough, then sang away to the hit into Nick Carter’s microphone.

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Justin Segura

Justin Segura

Justin Segura

The epic boy band showdown came just days after Bass’ bandmate Joey Fatone also attended the show, where he too was pulled up on stage to be serenaded by BSB. Fatone went one step further by scoring a smooch from Carter mid-song!

Fans will have to wait until April 12th -- when BSB kicks off their next set of Vegas shows -- to see if the rest of *NSYNC makes an appearance.